1. Field of the Invention
The present invention relates to an optical information recording medium (hereinafter sometimes referred to as an optical recording medium) containing a certain cyanine dye in the recording layer. More specifically, the present invention relates to an optical recording medium used in a method for directly recording information by laser beam and the like and regenerating it by change of the reflected light.
The optical recording medium of the present invention may further contain a quencher.
2. Description of Prior Art
Heretofore, optical recording media where a thin dye film is used as a recording layer have been known (for example, Japanese Published Unexamined patent application No. 16948/1981). That is to say, this kind of optical memory media is equipped with a reflecting metal film between a substrate and a thin dye film recording layer, and recording and reading of information are conducted by irradiating them from the side of the recording layer with laser beams at the absorption maximum. However, there are problems in such optical recording media including errors in recording and regeneration of information which tend to occur as a result of dust and the like which sticks to the recording layer because protection of the dye recording layer is difficult. Other problems include the fact that the composition of the medium is made complicated since a reflecting metal film is necessary for utilization in a reflection type optical recording medium; the sensitivities of recording and regeneration are not adequate; and the information recording medium itself cannot withstand long term preservation.
An optical recording medium of the heat mode type utilizes recording light as heat. An example of such a medium including the well known pit-forming type of the medium where information is recorded by melting to remove parts of the medium with recording light such as a laser which forms a pit, and the reading of a record is conducted by detecting this pit with reading light.
Various dyes or combinations of dyes and resins have been used in a recording layer of such optical recording media. However, one drawback of such optical recording media have is that the sensitivity of C/N ratio thereof is lowered by repeated erasing, erasing. Other problems include repeated irradiation of reading light or long term preservation. Therefore, in order to improve light stability of the dye and to especially prevent decolorization owing to reading light (regeneration deterioration), it has been proposed to use a dye and a quencher together (see, for example, Japanese Patent Published Unexamined Application Nos. 162691/1985, 201988/1985, 203488/1985 and 257290/1985).
However, even by combination with a quencher the durability of the optical recording medium against reading light, or stability thereof in long term preservation has not yet adequately been satisfactory from a practical point of view.